Ovulation Calculator

our ovulation calculator helps you work out when you're most likely to conceive a baby. simply tell us the date your last period began and how long your cycle lasts.

everyone's cycle is different, so our calculator uses averages to predict your most fertile days.

first day of your last period

length of your cycle:

your cycle is the number of days between starting one period and starting the next.


20 30 40

Your next fertile days are between

5th and 9th of October


Click here to find out more about getting pregnant

How Does the Ovulation Calculator Work?

The majority of women ovulate around 2 weeks before the first day of their period.

By simply inputting the first day of your last period and cycle length in the calendar above, our ovulation calculator will work out your most fertile days.

This 'fertile window' is the time leading up to ovulation and is the best time for you if you're trying to conceive.

How Does the Menstrual Cycle Work?

Alongside using our handy ovulation calculator above, understanding your menstrual cycle can help you work out when your most fertile days are and when you’re most likely to get pregnant each month.

learn about your menstrual cycle

The menstrual cycle is your reproductive system’s series of monthly changes or, in other words, its repeated regular pattern of events – and it’s all controlled by hormones.

For most women, the menstrual cycle lasts between 21 to 40 days.[1]

Each cycle begins on the first day of your period and continues to the first day of your next period, normally following this sequence:[2]

  • Hormones stimulate your ovaries to produce mature eggs
  • The lining of your uterus thickens with nutrients and blood to prepare for a fertilised egg
  • One of your ovaries releases a mature egg (ovulation) which travels down the fallopian tubes and into your uterus
  • An egg waits for about 24 hours in hope of being fertilised by sperm
  • If the egg is not fertilised it will disintegrate, your hormone levels will drop, and the womb lining comes away. Your period starts and a new menstrual cycle begins.

  • When is the Best Time to Conceive?

    If you’re trying to conceive, you’ll want to make sure you give yourself the highest chances of getting pregnant.

    Your monthly ‘fertile window’ is only a few days – about five days leading up to the ovulation[3] and the ovulation day itself – and that’s the ideal time to make a baby.

    One of the best ways to increase your chances of conceiving, however, is to have regular unprotected sex throughout the menstrual cycle.

    Sperm can survive and remain fertile for up to seven days, so regular sex will mean there is a higher chance for sperm to be waiting to meet the egg when it is released.[3]

    If you’re a dad trying to conceive (hello!), we’ve written a guide on baby making specifically for you, too.

    How Do You Spot the Signs of Ovulation?

    There are plenty of signs your body can give throughout the menstrual cycle to help you identify your ovulation day.

    Signs of ovulation include:

    • Changes in cervical mucus
    • Increase in basal body temperature
    • Breast soreness or tenderness
    • Pelvic pain and cramps[4]
    • Libido changes
    • Changes in the cervix
    • Heightened sense of smell
    • Light spotting or discharge

    Not every woman experiences ovulation in the same way but by learning to recognise the normal changes your own body goes through, you’ll be able to time baby-making accordingly to improve your chances of success.

    If you are lucky enough to have a regular cycle, it’s possible to work out when you’re likely to be ovulating with a few numbers.

    Typically, the egg is released between 10 to 16 days before your period shows up.[4] Remember when that last happened? Know your usual cycle length? Then you can find out when your ovulation day will be, either manually or by using our ovulation calculator above.

    Want more information on the main signs of ovulation?

    Keep reading!

    1) Cervical Mucus Change

    Around the time of your ovulation, changes in the consistency and appearance of your cervical fluid, i.e. vaginal discharge, can be expected.

    Look out for clearer, wetter mucus[4] and for when there’s more of it than usual – it makes the sperm’s access and journey through to the uterus and ultimately to the egg a lot easier. This is when you’ll be most fertile during your cycle.

    After ovulation has occurred, the cervical mucus will then become thicker and stickier – and not so welcoming to sperm.

    2) Body Basal Temperature

    After ovulation happens, women’s basal body temperature usually increases.

    This is the temperature of the body at rest (BBT), and it can be a good indicator to track where you’re at in your menstrual cycle. You can do this by using a thermometer and checking your temperature daily for a sustained rise.[5]

    Typically, right before the egg is released, your basal body temperature will slightly decrease only to be followed by a sharp rise – and this should last until the end of your cycle.[6]

    For a better prediction, you may want to keep the thermometer at hand over the period of a few months – it’ll allow you to learn more about how your body normally behaves during and after ovulation.

    basal body temperature

    3) Breast Soreness or Tenderness

    Some women experience breast pain or discomfort as the result of normal hormonal fluctuations of the menstrual cycle.

    Around the time of your ovulation, there will be more oestrogen in your body, which may cause you to feel different sensations in your breasts.

    4) Pelvic Pain and Cramps

    Some women experience pain when ovulating. Medically, this is known as Mittelschmerz, which is the German word for “middle pain” or “pain in the middle of the month”.

    Pain is usually felt in the lower abdomen (just inside the hip bone), on the left or right-hand side depending on which ovary is releasing the egg.

    Mittelschmerz can last from minutes to a couple of days and can present it's signs and symptoms in different ways – from cramps to an uncomfortable pressure to a sharp twinge.

    It’s not certain when exactly this happens in the cycle, but one theory suggests that the pain is linked to the moment when the egg breaks through the ovary’s wall, releasing a small amount of fluid that may irritate nearby nerves.[7]

    5) Libido Changes

    A woman’s sex drive usually hits its peak during ovulation, which happens around 12-14 days before menstruation.

    During this time, levels of oestrogen increase, causing an egg to be released for fertilisation. This means you’ll be in the mood to have sex at the same time you are most likely to become pregnant – clever, eh?

    Once your period arrives, you’ll notice a drop in libido – this is due to plummeting oestrogen levels. If your sex drive doesn’t shoot up during ovulation, don’t worry – everybody is different, and this isn’t a sign that you are not fertile.

    6) Changes in the Cervix

    Changes in the position and feel of your cervix can be a sign that you are ovulating.

    During ovulation the cervix rises and opens, becoming soft and wet to the touch – this makes it easier for sperm to enter. After ovulation the cervix lowers, becoming hard and dry to the touch – similar to the tip of your nose.

    To find out whether you might be ovulating, insert a clean finger inside your vagina until you reach your cervix, which feels like a protruding nodule. (During ovulation, you will be able to insert your finger further as your cervix will have risen).

    ovulation calendar

    7) Heightened Sense of Smell

    During the latter half of a menstruation cycle, many women’s awareness of odours becomes heightened, especially to male pheromones.

    This is only natural – when the body’s most fertile, it can give a potential partner of the opposite sex a more attractive fragrance like a special, baby-making perfume.[5]

    8) Light Spotting or Discharge

    The sharp drop in oestrogen levels immediately before ovulation can cause the inner lining of the uterus to shed.[8] This can then lead to blood showing together with cervical mucus, which is often called light spotting or ovulation discharge.

    Much lighter than a period, ovulation bleeding usually lasts up to two days; tracking its occurrence in the menstrual cycle help pinpoint the period when you’ll be most fertile.

    9) Ovulation Test Kits: Hormones in Urine

    Keeping track of all the changes that happen in your body pre, during and post-ovulation can be quite tricky, especially if you have an irregular menstrual cycle.

    That’s why ovulation predictor test kits can be so helpful – they identify the days when you’ll be most fertile by monitoring the changing levels of hormones present in your urine.[4] A small amount of the luteinising hormone (LH) is always present in your urine, but one or two days before ovulation the amount of LH surges, which triggers ovulation.[9]

    Some tests also measure a hormone called estrone-3-glucuronide (E3G). This hormone, which is produced when oestrogen breaks down, accumulates in your urine around the time you ovulate.[10]

    Ovulation test kits can be bought from chemists, supermarkets or online and are easy to use. To know when best to test your urine, you’ll still want to keep an eye out for other potential signs of ovulation.

    Having Trouble Conceiving?

    Most women get pregnant within a year of having unprotected sex regularly, but sometimes this isn’t the case. Having trouble conceiving can be quite frustrating and affect your relationship.

    Examining your lifestyle and health, along with using a combination of the above-mentioned methods and ovulation calculator to predict your ovulation day can help improve your chances. It’s a good idea to see your doctor if you haven’t conceived after a year of trying.

    Read More:

  • Preparing for Pregnancy
  • Early Signs and Symptoms of Pregnancy
  • A Dad's Guide to Conceiving

  • Approved by: Elizabeth Day - Mothercare's in-house parenting consultant for 15 years. Experience; NHS maternity nurse, children's centre support worker, degree in clinical and biopsychology from Birkbeck, University of London, degree in child development from the University of Nottingham.

    Last reviewed: July 2019


    [1]. Periods, NHS, July 2016

    [2]. Periods and fertility in the menstrual cycle, NHS, July 2016

    [3]. When am I most fertile during my cycle? NHS, May 2019]

    [4]. How can I tell when I'm ovulating?, NHS, May 2019

    [5]. Signs of Ovulation, The Bump, [Accessed June 2019]

    [6]. Basal Body Temperature, Flo Health, June 2019

    [7]. Ovulation Pain, NHS, July 2016

    [8]. Ovulation Bleeding, Flo Health, May 2019

    [9]. How to Use Ovulation Test Kits, Baby Centre, September 2017

    [10]. Ovulation Urine Test, FDA, April 2018